Gabriel Carter joined the sandbag brigade this spring in the Fargodome and helped build an earthen dike to protect a relative's home in the flood-prone Oakport neighborhood north of Moorhead.

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While he was stooping, shoveling and maneuvering a loader during the Red River flood fight, the North Dakota State University student made a connection not all are apt to reach.

"This is what climate change looks like," he said. "It's definitely a consideration that I make."

Many experts said climate change, with its rising global temperatures, produces more volatile and extreme weather -- including more floods and, conversely, more droughts.

Federal studies

Amanda Staudt, a climate scientist for the National Wildlife Federation, said government studies have shown Midwest flooding is on the rise.

"There's definitely been a trend toward heavier rainfall events and more snowfall events," she said

. In the Upper Midwest, the number of days with more than 4 inches of precipitation has increased by 50 percent over the past century, she added.

Even more important, wet spells are more likely to linger, sometimes resulting in damaging floods of the kind seen this spring in the Red River Valley, last year in Iowa, and the Mississippi River flood of 1993, Staudt said.

A study by the National Oceanic and Atmospheric Administration found a 20 percent increase in 90-day periods with precipitation totals at the top 5 percent of historical averages.

That's what happened in the nine months leading up to the record crest March 28. Fargo saw 25.26 inches of moisture from July through March, swamping levels that produced major floods in 1897 and 1997.

Topography factor

Staudt acknowledges that the Red River Valley's flat topography and other factors, including its northward flow, mean flooding is built into the landscape.

Also, scientists and environmental activists said no single storm or disaster can be attributed to global warming.

"On a micro level, I can't prove to you that a particular event is climate change," said Genevieve Thompson, executive director of Audubon Dakota, which has a Fargo office.

But not everyone is willing to correlate the undeniable rise in average temperatures that have been observed around the world with increased precipitation.

Adnan Akyuz, North Dakota's state climatologist, has documented the rise in temperatures throughout the state and a corresponding longer growing season.

But Akyuz believes the rain and snow that fall in North Dakota primarily are connected with surface temperatures on the Pacific Ocean, with its alternating El Nino and La Nina patterns.

His predecessor, John Enz, state climatologist emeritus, flatly rejects greenhouse gas accumulations as the cause of global warming, which he suspects has more to do with solar activity.

"I did not think it was climate change for a minute," Enz said of the spring floods.

On the other hand, Allan Ashworth, a paleo-ecologist at North Dakota and a onetime climate-change skeptic, believes global warming could be intensifying the natural pattern of wet and dry cycles that are so prevalent on the northern Great Plains.

If so, that would amplify already extreme droughts that have particularly plagued western North Dakota over the ages, said Ashworth, who has charted drought cycles from tree rings.

Ashworth notes that the average annual temperature in all corners of North Dakota increased 1.3 to 1.4 degrees over the past century, a rise consistent with the warm-up observed around the world.

"It's not only the poles, but it's happening here in North Dakota," said Ashworth, who has taken part in scientific expeditions to the South Pole for more than 15 years.

Will Gosnold, a geophysicist at UND who has studied climate change for more than 20 years, said flood protection plans should take the implications of more frequent and extreme floods into account.

He co-authored a study published in 2000, in the aftermath of the devastating 1997 Grand Forks flood, that stated flood protection plans must more accurately reflect climate cycles and land-use changes, including field drainage.

Flood mitigation takes its cues from flood predictions, which average river levels over recorded history. That tends to understate the tendency for catastrophic floods during wet periods, Gosnold and his UND colleagues argue.

Thus with the wetter cycles that are expected to recur from global warming, the Red River Valley is likely to face more floods of the magnitude of 2009 and 1997, which echo epic ancient, or "paleo," floods.

"We face a dilemma in that our flood mitigation program is based on floods that do not cause much damage and ignores the floods (paleo floods and other extreme floods) that cause the vast majority of damage," wrote Gosnold and his co-authors.

While acknowledging that not everyone agrees that human activity -- the burning of fossil fuels -- is the root cause of the long warming trend, Thompson said the nation must be willing to confront the harsh reality.

To curb greenhouse gas emissions, environmental advocates say it's critical to switch to renewable energy sources, such as wind and ethanol made from plant cellulose -- industries with great economic potential for the region, and other environmental benefits.

"Even if you can't all agree on the source, you can agree on the symptoms," Thompson said. "We better be ready. That's why it's useful to learn from this flood."

The Forum and the Herald are both owned by Forum Communications Co., which owns the Herald.